Multioffice telephone system



g B. D. WILLIS MULTIOF'FICE TELEPHONE SYSTEM Filed May 10, 1922 4 Sheets-Sheet l -Im r 11 Dr- Bernard D. M12115 Z rr;

1,6 8, 2 Aug. 9, 1927. B. D. wH-Lls 3 38 MULTIOF'FICB TELEPHONE SYSTEM Filed May 10, 1922 4 Sheets-Sheet 2 Inuen ZU Bernard .D .lnfilhs 4 Sheets-Sheet 3 B. D. WILLIS MUL'I'IOFF'ICE TELEPHONE- SYSTEM Filed May 10. 1922 m Q L 1T M 0.

Aug. 9, 1927.

InuenZmr- Barnard lllnmhs Z. M 5m Patented Aug. 9, 1927.

BERNARD D. WILLIS, or" OAK- ARK, ILLINOIS; assIGNoieBYmrEsN-ri ASSIGNMENTS, "r AUTOMATIC ELECTRICINCL, or 'cmcaso; ILLmoI'sfiacoRroRA-rmrr or DELA- WARE.

mmromcs TnLErmoNE SYSTEM.-

Application: filedMay. L0, 1922.- Serial -NoL-i 559,689.-"

- inventionrelatesin otfice telephone systems but more particu larly toisuch systems as comprisewin zone network oli'ices; or= exchanges of .tWQ- dii-j frentkinds, the-ofiices' oftone, kind. manual ofliceswherein connections are com}. pleted by operators, while the: other kind of ofiices are automatioofiices in which .corinections are completed by meansofhautomatic. switches, and the object o'fgthe invention-' is to' provide newand improved. circuit arrangements for. handling -interoffice calls betwecntheautomatim andi-mane uafl exchanges. a

Systems having botlr kinds; of. exchanges; as above pointed out are becoming quite, common and may-arise either by consolidation of existing manual and automatic systems,.serving thesame territory, or bythe process of. changing over a manual system to: an. automatic. system. Usuallyzin-the latter case only one'ofiice ata time-is-'converted from manual toautomatic and-:it follows that during the period of transition there will necessarily be bothJ- kin'dsof ofiices in operation. However the above sitn-- ation may arise, it is necessary.- toxprovide suitable circuit arrangements .-for handlingcalls from the -manual. ofli'ces to theautomatic ofiices, and'fromthe-automatic ()filCQS: to the manual ofiices. The present invention is concerned only with the latterclassof calls,and provides certain improvements in a system. comprising automatic to'manual trunks which are accessible to selector switches in the automatic ofiices-andtermL nate-in-plugsin front of av B operator at themanualiofiice, together with call registers for registering the-digits in; telephone numbers called by automatic-subscribers when the trunks are taken-for use, and an.indicat-' ing deviceupon which such numbers areshown to'the operator-one after the otherimproved. call register equipment, there being agroup of relays provided to register each. digit.- which-take-the place of the step by'step switches formerly used for thispur- I 6. 1 i .1 t I .-..Another feature; is theprovision of z a pirfeselecting; line -.s witch.- ifor. .preselecting; idle v call regis ensets, thus .reducing-ito .a ,mini- Inun the. ftime required) to connect with an idle call. register. set after the, cord-has been. seized fand inithis. way reducing; the possi.- bility, of, .mutilating, a call by the subscriber dialjingihe second digitbeforegan idle call Register hbe n. ;s .z d

ioncogt s w isqnductprfl n i itc tf.b

tween the mannal-, and..'automa-tic, exchange having s QQiahe mh mwi h om n-g o p husying-conductor, which-is common-to a group. 'oLtru-nks andg whicli makeS-JJhe trun-k group. busy, either,;i f- ,th e operator leav'es hertposition, or'itt all calkregister sets of the group arezina Various otherdetail improvementsw'ill b6: further pointed out-in the detailed specification which. follows.

-;j1'.;n ,the-; drawings,. comprising Figs l, 2, 31 anidri, there. 18 shownby means i. of); the usual circuit. diagrams the -apparatus and circuit connections thereof which is. involved-in a complete. connection extending. from the automatiesubstatiom A. .Fig. 1, to a. manual substation: A, Fig.;. 2; The apparatus indicatedjin Fig. 1 is located in an...auton1atic exchange,,while the apparatus indicated in Figs. 2,33,.and Li's-located in a manual exchange. Inasmuch as the automatic switch-- in; equipmentdtself and the manual equipment are bothcwell-known-and oftheusual type. node-tailed description of the mechanical features of this apparatusnwillibe given, except in so .f-aras-it'is found-convenient or necessaryto'doso in the explanation of theoperation of the circuits.

Referring. to Fig. 1. the substationA is one of a plurality of' ordinarypautomatic substations terminating. in the'automatioexchange previously referred to, and'isprovidedswiththe usual talkingequi-pment and ringer; and also with a calling device ofwell known type'whichis indicated by; the referencecharacter S, through the medium of which the subscriber controls the central ofliceswitches.

The-line conductors 11. and 12.eXtend-to the exchange where-they terminate in the line switclnC, which may be briefly described as a rotary line switch whose movexchange. In Figs. 3 and 4 I have shown able terminals or wipers have no normal poone of these register sets complete. It comsition, and which have movement in a forpnises register controL-switch RGSy Eig. 3, ward direction only. The construction of a and register relay groups R and "B", Fig. 4. line switch of this type is well known in the The register control switch RCS, which may art, and itsfunctiomalso wellunderstood, is be described briefly, consists essentially of to e xt-end its associated line when callingto vviiperg355fand its associated set ofbank conan idle trunk line. In carrying out this obta cts, togethehwith a stepping magnet 359 ject, a plurality of theses individuallineyfor advancing zthe switch wipers, and a reswitches are given access to a group of trunk lease magnet 358 for restoring it to normal. lines extending to first "-s'electo'r switchesi A set o'f rotary-ott-inormal springs 357 are One of the trunk lines to which the line included in the circuit of the latter magnet switch C has access is'shown 'in the drawandfare' 'closedfon the firstmovement of the ing as extending to the first selector-$1); switch; i i Q which is a vertical'and rotary 'selector of the T-he register sets comprise groups of [re-' well known Strowger type. "In a multi-ofiice la'ys, therefbeing: agroup -for each digit in system ofthe kind herein contemplated the the called number."The'arrangement-is suchfirst selector switchesane' nsually known as that the-various digit lamps are 'c'on'nected office selectors and the'selector D in common' up" by the'bpera'tioh of oneor'morc relays of with a plurality of similar selector'sfhas ac a group. A switching relay -o'f'each group is cess to a plurality of groups of trunk lines, also'operated to prepare-the next group, and each of which groups may extend to'a difi'en so on. W'hen a -final digit hasbeen' set up ent oflice or exchangein the' system. Some the-switching relay 'of thelast-groupcloses of these groups of trunk lines may exte'nd a" circuit to cause a consecution control to automatic'exchan' es whileother roii s sw'it-ch to selct the reisterset-whichisin b- 7 b L may extend to manual'excli anges. use after which a circuit is closed-to light "A trunk line in one'oftlielatter groups" the ca llindicating 'lamps 'corrcs' 'iondingto shown in the di-awing a'nd 'compri'ses"the the d'igitsetn i repeater E and the trunk line conductors p flTh'e'indicating device by' m'eansof which 130 and l l1w ich extendt'o'the manualexf called'telepho'ue.uuinbersare shown to the change in question and there terminatenn operatou'is shown iu counc'ct-ion with-the the plug ending cord circuit O;"Fig.'2. The register sets-shown in-Fig. 4. 'It comprises. i

cord circuit 0 isone of a plurality of simiessentially,"a'plurality'of group's ot' switch lar cord circuits, at a B operators position board lamps, there being one grou rof'lam 'm in the manual exchange and constitutes the for each registerre'lay group in a" register means whereby the trunk line shown may be set. It will" behnderstOod'thatthe lamps connected by the'operator with any one of have the function (if illuminating' the digits the manual lines terminating" in the manual of the called nun'ibers and causing them to exchange. One Of theselines is 'theline of stand out-so as to be readily distinguished. substation A, which with its associated line Thedigits' are preferably marked in black equipment is shown at the right of'Fig Q. on the'rever'se side of a white semi-trans- The repeater E is an automatic impulse parent surface and ordinarily are not very repeater of the general type in commonuse conspicuous. But when the switchboard and in addition to repeating operating imlamp immediately behind any character or pulse to the distant manual exchange, profigure is lighted such-character or figure rides holding circuits for the automatic will stand out very clearly and is read with switches, and thus renders it unnecessary to great facility. The lamps of the indicating use more than two conductors for the interdevice are wired'to contacts on the relays of oflice trunk line. the register set shown, and are also wired to From the foregoing it will be understood similar contacts on the relays of the other that the operation of an office selector. such register sets at the position. as the selector D, in response 'to the calling As stated hereinbefore, there area pl L of the first digit in the telephone number of ity of register sets providing for the regisa line in the manual exchange, will result tration of a plurality of calls simultaneously in extending the connection from the line Of or close together. These registered calls are the calling automatic subscriber to an idle displayed on the indicating device one after plug ending cord circuit in the manual eX- the other as fa=t as the operator can complete change. In order to take care of the rethe connection by plugging into the multiple maining digits in the numbers there is projacks which correspond to the members disvided for each B operators position a pluplayed. In order to switch the calls over rality of register sets as liereinbefore stated, onto the indicating device in succession a soeach set being capable of registering all the called consecution control switch is provided. digits in a telephone number, with the ex- This switch is hown in Fig. 2 where it is ception, of course, of the first digit which indicated by reference character COS, and controls the office selector in the automatic comprises a. single'wiper and bank of contints- 219 shown in the-drawing: The-switch 66$-is =mechanicalK the same: in; eonstrum tion as the-rotary'line switch iGyFig 1,.that i'sgqits-wi'peie have no normal position-and circuits, however, are changed and 'will be describedhereinafter:

- Each register set is? provided with-a time Controlled switch" whit-brimthe r case-oi: the:

register-setshown in Figs. 3 and his indicated-by the reference characterP, Fig. The switch P may be similar in con.=.truction the register control sinitch but-'- is operated .r'y timing'mechanism instead of byx'means of iinpulses -eorresponding to -digits' in: theregistemsets ea'chvcordYcibcuit is- 'provided:

with an: individnalphingeli type line l switch which is -maintained;i po'siti onecl before an idieTegistersetnvhen not ini-nse by-a masterswit'chi These Iine'sWitehes'ha-Ve' common access to all -ith'e register setsf T he re'ferenoe character C"; Fig; 3,i indicates-a plungertypeline switch-which is iiidiividua-h tothe layout of operation cord' circuit Oi. '2; andnwhi'ch: .has access to theregister set shown in" the drawings, assumed 'tobe'the-fiish a-mdialso tmthe otheit registersets which are providedat the B operators position in which the cord circuit 0 terminates, Line switch! 6' and "the master switeh MS, are 0t weli1-linown construction andfunction and on thisaccount' will notfb'e described in' detail as to their mechanic'a-l' operationi 1 Having de fcribed in a general way; the the system herein diselosed.,! the of the circuits will now be described more indetail. itbeing. assumed for this purpose that the subscriber atzsubstation A, Fig. 1, desires to obtain a connectionwitlr the. manual snb=criberat substation A, Fig.

2; whose telephone number, it will beassumed, is 345. \Vhen the. receiver'is removedat substation A,- a'circuit is'completedover the line conductors 121' and 12bforrthe= line-relay 14 of the individual line switch 2 C. Upon energizing, the line: relay completes at its armature a circuit which extends through the switching grelay 13 and the stepping magnet 15 in sevie'! to battery;- and at wiper 2i; to-tho above circuit at'a point-midway between the switching relay and the said stepping magnet. The operationnow depends upon Whether the first selectortrun'k with which the wipers-:of tl1e:.-li11e: switch 'are inconnecticn is busy or is; not

its armx-itare 19 connects the test busy If this-trunks line is; busy. thev test contact 31 associated: thJer-e-witlrrwitl have, a ground potential-'upennit, the switching'-relay-13 williibe short eiicuitedytllid the stepp ng 15,11 whichinterruptssits own 7 circuit; wilt operate asfa bUZZBIJtO advancether-wripers'2fi 2 inclusive; step by step in search ofran' idletrnnk line. 1 -'Ehis'-operation will continue -aslmi'g as therteet wiper: 26 continues to engageigrounded'.or busy test contacts; However; wewmay-= assume that in thepresentca'se when the caillisinitiated-the selector D" is; idie and the testcontact: 31-v th'erefocei is not gro ended: Under these oil; cumstances when the: line relay 14. is energizedthe switching relay- I3 fis energized immedia'telyr v afteifwandgxwith the resultithat. theline conduotomll 'a'nd 12/a1'e disconnected f-rona-th'e winding of. the lineurelay .142 and. from-ground; respectively; and; are ex t-ended by way ofziammature 16 .a nd*:18 and-:their' working conthctsewipers and: 27. ..bank contacts -"andi32; anxileanmatureszfit) and 6% aneli r their restin gf 'contaots,:to the up per. and lower windings of the: line: relay-rd the selector D.

As soonias -me line: is-vextende tothe selector D 'as-above-de'scribed; the" line relay 50 willl beenergizedaand willi clo'se the e-ircnit" ot' the: slow acting? release! relay 51 Upon energizing, the; latter relay prepares the circuitsot the selector 'iitri operatiom: init's vertical movement 'in thei usual manner, and 'aisoicompletesi aa-lroldin'g: circuit extending b'acktothe lizne switch: (3 ELSi-fOliOWSZ ground, working contact-of armatur'e fit and the said:armatrwe',-.coniiuctoi: 6%, bankzcontaet- 31, test wiper: 26*, armature 17. andits working contact; winding: of the switchi: s relay-13;; and: thewindin'gr-ofr-the stepping magnetlfi: tin-battery; 'I-t' 1si1ndei'stood that the ahoveholiclii n-gcircuit is=c0mpleted before the slow actingrelay, 14; has .hadrti'me to deenergize=-. In addition to maintaining the switching: relay"energized,. the holding circuit also serves: to provide ground to the multiples-of test:contaet-31 and also to thrmultiple test'zcontacts in-wh-ich the private normal 'condnctor28 tenminates inthe banks of the connectors which have access to the line of substation A. thereby guarding the connection: against intrusionin the customary manner; Y

The calling subscriben-may now operate his callingedevice S- in accordance with the first digit of the desired number. Three interruptions are thereby producedin the circuitof theline-relay 50, and the said relay: is accordingly threetimes deenergized momentarily, transmitting at each deenergizationnan impulse otcurrent through the slow: acting series i'elay-52-and the vertical magnet 56 to battery. By theyoperation of the vertical magnet the selector shaft is raised tlmee steps whereuponlthe wipers 70-72,-= inclusive, will! be.- xstanding opposite the level of bank contacts in which are termi-i nated the trunk lines extending, to ,the; manual exchange; -The slo'w acting :relay 52 is energized in series with the vertical' nagnet, retaining the armature attracted hroughout the vertical movement. of v the- ,witch, and upon the closure of the vertical off normal springs 59 completes-a circuit for the stepping relay -Uponienergizing, =relay 53 prepares a circuit forithearotary magnet 54 at its lower armatureand-at its upper armature establishes a=loclrii1g circuit for itself. At the end of the vertical movement: of the switch the slow acting-relay 52 :is deenergized and closes the circuitiof. the rotary magnet, which is-thereupon-energized to ad-; vance the wipers 7072,- inclusive, into'*engagement witlrthe first'lset of bank contacts in the level opposite which' they are-iraised. The rotary magnet 54 also breaksthelock:2 ing circuit of the stepping relay- 53;;whichaccordingly deenergizes and breaks theucir-l cuit of the rotary-magnet, which-thereupon deenergizes: also and againcloses its/interrupter contact. ii

The operationnow dep'e'nds' 'lupon whether the trunk line witli'wh-ich;thezwipers have! connected is busy or ;is%no't:;:busy; If this trunk line is busy the test contact associated therewith will be grotinded and-the stepping, relay 53 will be energized .1 over a circuit which extends byway ofthe :test? wiper. 71, armature 61 and its restingecontact, inter rupter contact of the-rotary magnet,:ofi 'nor? mal springs 59, and-the winding of ,.the stepping relay 53.to-battery. 'rThe stepping. relay will therefore again close the circuit of the rotary magnet 54 which will operate to rotate the -switch wipers into engagement with the next set of bankco'ntacts. This operation in which the stepping relay and the rotary magnet are alternately energized and deenergized will continue as longas the test wiper 71 continues to engage grounded or busy test contacts.- In the present case'it will be assumed that the trunk shown in the drawings -is the first idle trunk line, andwhen therefore the test wiper -7 1: arrives at test contact 74 and the rotary magnet is deenergized, the stepping relay 53 will not again be operated, but instead the switching relay 55, which heretofore hasv been shortcircuitcd, will be energized by current flowing over the following path: grounded conductor 04, winding of the switching relay interrupter contact of the rotary magnet 54. off normal springs-59, and the/winding of the stepping relay 53 to battery. Owing to the high resistance of the switcl1- ing relay 55. stepping relay 53'is not operated. Upon energizing, relay 55 disconnects the incoming line conductors from the windings of the'line relay 50 and extends them by way'of arniatures and 62 and their working contacts, wipers and 72, bank contacts 73 and 75, trunk conductors; 76. and 7,8, and normally closed COIltELCtSnOf therrever'sing relay 100 to the upper. and

lower windings of the line relay 101' ofthe i repeater E. When the line is extended to the repeater. as-above explained the line relay 101':is energized and closes a circuit of the. slow acting release relay 102. Upon energizing, relay 102- completes a holding circuitf-extended-back to the selector and line switch G as follows: ground, armature-112and' its working contact, conductor 77, test contact- 74, .test wiper 71, and the armature Gland its working contact to conductor 64, where, itrjoins' ,thepreviously described 'holdin cir-.- cuit-extending back to the-line-switc (l; The-above described circuit serves to main tain-re'lays 55 and13 energized throughout, the duration of the connection. I In addition to closing the holding circuittor -the automatic switches -C and-D, the-relays 102 0f :the repeater E prepares 'a-lcircuit atv-it's armature 115 for the ,slow acting relay;

* 103-, closesa circnit-atits armature 114 whichen'ergizesthe polarizing windingof the eleclro-polarized relay 105, and at its armature 11-3conipletes "a bridge across the trunk; conductors 130 and 131 which may-betraced over :the following path: conductor 130,. armature 113 and its working contact, tarmature 116 and its resting contact, upper winding ofthe electro-polarized relay 105, normally closed contact springs controlled by 1 armature 108' of relay 100, right hand winding of the impedance coil 106, and armature 111-and its working contact to the conductor; 131; I By the closure of this bridgeacross the trunk line acircuit is completed for the double wound line relay 204 in the cord circuit O, and the said relay 204 is therefore operated.

' When the calling line is extended to the line relay' 204 as above explained, the said line relay is operated, and completes an energizing circuit for the slow acting relay 203. Relay 203, on attracting its armature 215, closes one point in the circuit of relay 201, at its armature 217 closes an operating circuit for'the individual line switch C which extends as follows: ground, armature 217 and its working contact, armature 213 and its. resting contact, conductor 234, resting contacts of spring 348 controlled by the armature 360 of switch C, winding of line relay 301 to battery. Line relay 301 energizes over this circuit and at its armature 349 completes a circuit for the pull down winding 302 of the line switch C, which may be traced as follows: ground. armature 349 and its working contact, winding 302, conductor 333, armature 310 and its resting contact to battery. The closure of the above traced circuitcauscs the plunger controlled by circuit to maintain thegplunger Jinan opere ated position after the xii-mature 349 of' the line, relay i301 restores. This, circuit may the traced; from ground, armature "217 and its; working con t-aet, armature 213 and its-rest; ingcontact, conductor r234, @springs 348 and; 347,. holdingwinding 303 of linefswitch C- tobattery. The operation of the plunger caused the spri ng contacts 311,313,- 315, and 317to-en age springsi3l2, 314, 310, and 318, P 0 -.:"i [Ti-i, .-.i. .11: The closure otspringsffilj maaw com-. pletes a circuit overtheconductor 338 ex;

. tending to the nia'stenswitchqbank; contact upon which ,the master-switch, 1wipeiw337; is nowresting, for; energizing the start-ingrelay 3300f the mastewswitch MS. ,-.l1p0 energizing, the. relay 33,0 closes a circuit, fo the locking magnet335, which unlocks the master-switch shaft and: thus brings about the realign ment ofjall idle; line switch plungers in front 'of-the nel't idle call register set.. ,The starting relay 336 also closesma circuit for the openmain relay 334, which upon energizing, disconnects the common conductor 333 fromt-he negative pole of battery, in orderwto prevent any oi the line switches from. being. operated until the master-s witch comes to rest. 7

'Th'e closure of contacts 317 and 31-8 pre pares .a circuit for lamp L in the ,cord Cir-- cuit O, at contacts 311 and 312 a point in the impulsing circuit is closed, and atcontacts 31 3 and 314 a, circuit is closed for relay 306 in multiple with the holding winding 303 of line switch C. The operation of relay 306 closes another point in the impulsing circuit at armature 341 and its worklng contact, and at arn'iature 310 and its working contact a circuit is prepared over conductor 404 for the call register group switching relays 400 and 405, at armature 321 ground is removed from the hank con tactof the time limit switch P, and at armature 320 a circuit is completed for the stepping magnet 324 of the switch P which may be traced as follows: ground, interrupter contacts irl70,'comlucior 322, armature 323 and its resting contact, armature 320 and its working contact, stepping magnet 324 to battery. Switch P begins to operate to move its wipers 330 and 331 over their bank contacts, for a purpose which will hereinafter be described.

Everything is now in readiness for the transmission of the second series of impulses. The subscriber will now operate his calling device in accordance with the digit 4, which will cause the line relay 101 of the repeater E to fall back a corresponding number of times, which results in a. like series of inter ruptiona-of-v the circuit in theline relay 204; Each time line relay .204: fa.lls back -an in!- pulse -is' transmitted to stepping-magnet 359 over the; following circuitr ground, arms. tune-i218rof-llinerelay 204 and-its resting; contact, conductor 233., contacts 311 and 3E otzline switch-Gharmature 341 and its :worln ihg5;0011t1(;t,2 winding of relay- 1 305?, and a the winding; 0t stepping magnet ;359. to; battery.- The; first digit transmitted to .the :register sets being the-Jdigit :4, the .steppingmagnet 359.1; receives; at. impulses r which causes its; wipen355- t0 be set on its fourth .pair of bank contacts. zwhen thefirstimpulse; was transn i-ittegl over-rthe. iin pulsmg circuit the slow, relay 301 fwascnergized. ,This relayremains duri gieach r si i mp l an .v atei s. armature, 326 disconn c per 5- whi eheiswitch is r ta ing. 1- Myths te nati epfi i serie -.e impul he s ow aleyiwl; eee erg z -iandeat its mat re 32.6 -eclor et etltell si sisir ii ag und! rstingic etsstsiwiiee trii edihr armatur .72mi: re ay ,Q .-u-. s ss t re x 39 ,1 i a 'HFS rZ ZQ'F- :I Q$Q E .rbn ee tivipsrfifia, anre naaawt oni eo i329 a a Wendie rest essness n -t w d otrelaygltllto battery, .Qnlconipletion of eachers. c i e i t. rela s 41 nd 4 2* erg zedan, series.

he operation-bfa'elay308 completes'a. circuit forflrelay 309., traced from ground, armature 354 and its working contact, windingof relay 309 and. ottnormal springs 357 to battery.v .Bela- 3090 crates and at its armature 372 an its wor ing cont-act complctes a holding circuit for itself, at spring 3 28, and its back contact ground is removed froi'n relay 308 and at springs 328 and 329 acircuit is completed forrelease magnet 358 to cause the wiper .355 to be restored to normal.

.The relay 402, atits armature 403 and its working contact, closes a holding circuit for itself which may be traced as follows: ground, zu'mature 319 of relay 306 and its working contact, conductor 404, winding of relay 400, armature 403 and its working contact and the winding of relay 402 to battery. Relay 400 operatesas soon as relay 309 pulls up, being shunted out until this occurs, and at its armatures 407,. 423, 415 and 416 switches the register control circuits to the next and in this particular case last register set, it being understood that any number of register sets may be provided depending upon the number of digits in the called number.

The apparatus is now in readiness to re-, ceive the final series of impulses. The subscriber again operates his calling device, this time in accordance with the digit 5, which causes a similar operation of the line relay 101 of the repeater E, and line relay 204 of the cord circuit 0. The stepping magnet 359 of the switch RC8 is again'i-oper ated over the previouslytraced'circuit, this time" causing the wiper 355 to step to the-fifth-contact set, after whichi-the: series' relay '307 again falls back and this time closes'operating circuits for relays 417 and 418 .of the lastregister set. :ThesecircuitS may be traced =as follows:=ground, spring 328 andits resting contact, winding of relay- 308 ,'and armature 326 and its resting' conta'ct to wiper 355, where thecircuit divides, on'e branch ex-- tending over bank contact 381;- conductbr 481, armature 415 and its working-contact, conductor 483, armature 425' and 5 its Testing contact,- and the winding of relay; 417 10 battery, and the other branch-extending over bank contact 380, conductor 480; armature 416 and its working contact,' *conductor' 482, armature 484and its resting contact, and'the winding of relay 418 to battery.-- Relay*417-,' on energizing, completes a holding circuit. for itself which maybe-tracedas "follows? grounded conductor 404,; winding of' r'elay 405,:Working contact of 1 armature 420 and the said-armature, and'the wiiiding chewy 417 to batte'ry."A similar"'holdirrgfcircmt' for relay 418 is closedhvei' conductorf 404, winding of relay 405, Working'COiitaCt Qf'ar mature 419 and said arma'ti'ire, and the-Wind ing of relay 418 to battery. The release of the register control switch' isbrought about in the same manner as hereinbefore described by the operation of, relay 309 and release magnet 358. Switchingrelay 405 operates as soon as relay 309 pulls up, being shunted out until this occurs, and at its armature 413 completes a circuit for relay'305, froni', grounded conductor 404, by way of armature 413 and its working contact, conductor 414, resting contact of springs controlled by arniature' 361 of relay 305, winding 'of said relay to battery.

On energizing, relay 305 looks itself at armature 361, stops the operation of the timing switch P, at armature 323, while at armature 363 the conductor 284 is connected to ground, thus closing a circuit through the lamp L, Fig. 2, and the relay 262 of the consecution control switch CCS. By the closure of this circuit relay 262 is energized and lamp L is lighted to notify the operatorthat a call has been registered on the associated register set. in addition to the foregoing, relay 305 disconnects conductor 271 from ground at armature 365 and extends it instead to the winding of relay 304. Conductor 271 may be considered as a test conductor and extends to the first contact in the bank of the consecution control switch CCS, since the register set shown is assumed to be the first register set at the position. The other test conductors 272276, inclusive, are of course associated with the other register sets at the same position.

Assuming that no other call is being shown on the indicating device just at the present time the consecution control switch? CCS is immediately operated to switch the.- registered call over onto the indicatin de-'- vice. The operation is as follows: henrelay 262 energizes, it connects up the wiper: 264 by means of armature 266, and at armai ture 265 closes a circuit for the slow acting line relay 261. Upon energizing, the latter relay closes a circuit at its armature 268' which includes the switching relay 260 and the stepping magnet 263 in' series, and at its armature 267 connects the'wiper 264 to' the above circuit at a point midway between the said relay and magnet. The-.lattenop eration provides foradvancing the wiper 264 in case the contact with which it isin engagement is grounded, but it will beassumed'in the present case that the- \viper' is-standing on the first contact of the bankas-jshown in the drawing, and since the ground has been removed from this contact' by the energization of relay 305, no rotation of-the switch will take place. Instead, the switching relay 260, which is of high resistance is at'once energized in series with the stepping magnet 263, the latter remaining inoperative, and breaks the circuit of the line relay at armature 269. The line relay is slow acting, however, and before it .has time to fall back relay 304 in the regs:-

ter control switch is energized over the following circuit: from ground, by wayof armature 268 and its working contact working contact of armature 270 and the said armature. working contact of armature 266 .and said armature, wiper 264 and the bank contact engaged thereby, conductor 271, armature 365 and its working contact, and the windinr. of relay 304 to battery. Upon energizing, relay 304 locks itself to the grounded conductor 404 at itsarmature This operation connects conductors 404 and 271 together and a circuit is thus completed for supplying ground to the switching relay 260 in the consecution control switch 005. in order to maintain this relay energized after the line relay 261 has" dcenergized. Relays 305 and 304 in the master control switch are now both energized, and the c0n. .ecution control switch is in operated position (switching relay energized) with its wiper in engagement with the bank contact corresponding to the first register set. Other calls may be registered on the other register sets at any time now and when registration is completed the lamps L L etc. corresponding to the register sets in use wil be lighted, but this has no effect on the consecution control switch CCS. which makes no further movement until the call on the first register set has been disposed of.

Relav 304 is the relay which switches over the registered call to the lamps of the indicating device and the manner in which this sesaegasz his done' -livill-mcw :be peinthd rout. *When relayAOQ 'operated it prepared at its :armzitune485 'a CilCuit'fOI' iiIlGliCfiiOI lam 4-hlf the' first digitextending from common conductor 490.. armature 485 and its working contakihcrmatuces 186 and itsz restingk'ont'act; armature 487 .and its :rrestirrg contsa2t, immature #488rznd its :resting cont-act, can; dudes-1421, ilemp :4 to battery; *"zigVh'en -relay 917 and 18 were operated-s11 circuit iwvas =prepared fior lwmp 5 of the vlast dig it" circuit e'xtends 'firom the common -ioonchlctm- Q390,ia;mnature 412 and nits vrest-ing contact armature 428wand 2 its :restslmq- =contact eaa'mature '426nand' its working =c0ntact,: armature :427eanddts working contact-, conductor-i422, -lwmi 5 tp-'battery. Frrierww-z wFJWLhen ainnature 391 not :relay "304 ig attracted,-ground is placed on conduction lIrt Hfdllows; tlieue-fcrexithat \vitlr the register exielays in their present operatedipo'siticn cenductors421 and 4E22-xvil1 be grounder-ll causing-Ftheindicatinmlamps N0. :4 ithe first groupa nd'No. 5 lamn obthe Ilast groupdlo lliglit Ito inform: the operator that themtlled line inuinberis 45.- J,

lhe manner in which-theoperater handl- "the call thus displayed before he": will Y now b econsidere'd. WVh-en relay-304 ei t-h-e regs :ister controlsw-itch RCS ipulls up and closes aflcinciqitfifor displaying zthe=a'e .;u;ist-ered mum- !ber' to rtlie: operator, it also closes 3ft 1 its 1 irr maturc 393 a circuit for thetlrmik or ea-'11 signal: lamp L inthe =cerdci1'cuit' (),-:which may betraced ilSTlfiOllOWSt :from grouniliby :way of-"the working contact of a-r111 a:tu1'e 53-93 and :the said .aunature,= spring drank-cem- 'tacts- 31*8, Sand 317 of sWitChf- C-C conductor 5235', winding of-relay-202 armature 21.1 mid its 'resting'cont-act, armature .1222 'ua ntl tits 'a'estim'g contact, lamp L to battery. "By "the closure of the above circuit, lamp zL. which ,is'individual lO'fllllG- cord -'circuit iszi-ighted simultaneousl :with the; calllfi'mdieating zla mpsrthus enabling-theopemtor-to "know which one of :her :cord circuits is beina: used by I the automatic subscniber -'wl1ose wanted number'isat this particular. time being shown on the indicating :lamps. 'Ha-vving observed the number 45, and knowing by the lighting of the lamp L that the cord circuit Olis the one: in :use,"thc cperator 'will test the multiple jack of line number with the tip other-plug in the usual :manner, in order to find out whether 0! not lthc'li-neis busy. If the lineiis found to be IiIlEUSG, the plug will be inserted in a burr back jack. of well known form "and fun-:- #tion, iii order to give the-calling subscriber a'husy signal. Assuming, however, that the linc found to be idlel'the operator will ronce jineert the plug 'P in the jack -of the wvantedline, which intlle present case .is 'the jack J.

-- 'uAsasoonias-thenplug is inserted the jack La circuib-isicor'npletedffor the-sleeverrelay'209 insenies with the cutioiff znelay Q40 ofathe calledlin-e al'nd the; latter relay 'fis energized ztd-cl'ear; the :line =oi -itst'normal battery and ground connections ;in uthe usua'l ma-nner. :Rehrjfl 2094a energizedua'lsoandszit armature 227 disconnects: ithe operatorlsvhead set. At the -same "time :ata tuna times-227 xii-Dd 1229 the tip andigringi oomluctor s of :the. cordyare- .coninected throughsrtoutlie plug,:iarvd a ringing circuit: is estab'lished ovenwliich'i i rtging current :rfnom Z the: generator GEN is izprog'ected intermitteixtlptosignal the :cailed subscriber.

In :additioxi'to lthe functiens described; relay- 209 also ieloses'fa circuit for relay 207 :at Y armature 1 228.. Upon energizing, relay l207 opens lth Eeircuitef the cail'l signal lamp .Ii'f: atviarmature-222; and et armature 22E closes a circuit :for relay-201,: which includes "thei grounded sbonductor 1235.- Uponnener- 5? gizingpreliIy-QO l establishes. ai flocking circuit utter itslt ratiits'iarmatureflltl, and'lat thei'ba ck contact -:of+ithe sarne immature disconnects groundnfroin the holding conductor-234.

- fThe flash ioperatid'n v above 'imentione'd, beings labouh =tl1'e release of the :liine switch iCnand-the-cre'gister set upon whiohflthe called lnumber rwas registered, which will now be explained WVhen'Iground is disconnected hold winding iof line switch C. and "relay .sw itchr G zand itherela y 306 are restored :to normal. When -i ela1y 306-Jdeener'gizes at'armature 32llitzclosesia circuit forithere'lease magnet 325 .of switch :P, and :.at .armat ure 3fl9zmemovesk lground fromathe 'ht'ldirngcircuilsiof relay; 30451305, 400 arid-L405. fThc circuitofrthe 'releaseamagnet mf-thetimixig switch .P; ds -b'no'ken' 'when Wiper .330 1 moves oft itscentacti bank. f lhe'rregistcrset is now completely restored to normal in readiness "fortuse-in registering another telephone number.

l'Vhen ground. is disconnected from conductor Q84 lamp L is extinguishedyaznd in case there'ismo' lather-call Waiting. at this time relay 262' of the consecuti-on control switch CGS Will-be deenergized. If a :cnl'l iswaiting;whowever,:relayLQGQ will be held up in series with one ofthe other lamps shown, such aslamp I orl-a.=n-1p:L for example, and when relay-i260 ;faflls'1back, the line relay 261 will .again be energized. Since the first'ite'st contact inathe'lba-uk traversed by Wiper 264 has just been grounded by the=deenergiization of relay 305, the eperation =0f'the line relayr261 causes the consecution centrolwswitch GUS-t0 advance its Wipers into engag'eanent'WiuhIthe'test contact which is assooiatedmvith'ithe first register se upon which. aregifiered call is waiting...and it'hlS CZlli lSTt'hHIl SWltChedeOn to the lamps at the indicating device,:-the =same1ashas been described. e

" .Returninginow toFthecord circuit 0, it has been explained how the connection has been completed'to-the line of the called substation-A; and-ringing current is projected out over the called line to signal the subscriber. During the ringing operation a tone is induced in the left hand winding of the repeating coil of the cord circuit 0, by reason of the fact that the ringing circuit includes the upper right-hand winding of the repeating coil, -.and'this tone is audible to the calling. subscriber,-who is thus advised that the signalling operationis proceeding satisfactorily. The ring cut-off relay 208 isineluded inf-the ringing circuit and when the called subscriber answers, this relay pulls up and locks itself in energized position by attracting its armature 225, which operation includes the upper winding of the ring cut-off relayin the circuitof-the sleeve relay 209. -Relay 208 alsobreaks the ringing circuit at. armature 226, and at the worl ingZ'contact..-of the same armature finally completes the i talkin circuit. The transmitter at the called station is now supplied with talking current through the right- -hand windings of the repeating coil and through the upper and lower windings of the battery fe'ed' relay 206. Relay 206 energizes in the first instance through its lower windingalone, since the upper winding is normally short circuited inorder to .keep it out of the ringing circuit, but when the relay pulls upboth its windings are included in the battery 'feed circuit. In energized position, relay 206 closes a circuit for the reversing relay 205. Upon energizing re'lay 205 reverses the trunk conductors 1'30 and 131 as regards their connections with the windings of the line relay 204, and the direction of current flow in the calling line is thus reversed. The direction of current flow through the upper winding of the electro-polarized relay 105 at repeater E is therefore reversed and this relay is now operated. At armature 118, relay 105 places a shunt around armature 116 and its resting contact and at armature 119 completes a circuit for reversing relay 100. The operation of relay 100 reverses the direction of current flow in the calling line. This operation may be used for operating a meter, or for other similar purposes, and is provided in accordance with standard practice although it is of no utility in the particular system shown herein.

The required connection having been established, the subscribers may now converse as desired. When the conversation 1S finished both subscribers will hang up their receivers, and the replacement of the receiver at the calling station A causes the automatic switches to be restored to normal. When the receiver is replaced the circuit of the line relay 204 is broken, resulting in the deenergization of this relay and also in the deenergization-ofthe slowacting relay 203..

Relay 203, on deenergizing, closes a circuit for the supervisory lamp L at armature 217.

When the operator observes the lighted supervisory lamp L she will remove the plug of the cord circuit from the jack and relays 209, 208, and 207 are deener'gized and restored to normal. Bythe falling back of relay 207 the circuit of the supervisory lamp L is broken at armature 223. All the apparatus has now been restored and is ready for use in handling another call.

In case the operator should accidentally withdraw the plug from the jack before the automatic subscriber has hung up his. re ceiver, means is provided for flashing'the lamp L to call her attention to the error. WVhen the plug is withdrawn relays 209 and 207 are deenergized,-and-since relay 201 is now in energized position, the calling subscriber not having yet hung up his receiver, a circuit is completed for the lamp L which includes the interrupter I, and the lamp will be flashed to attract the attention of the operator. If the operator remembers the jack from which the plug was withdrawn she ,can re-plug immediately, otherwise she will plug into a special jack (not shown) which connects with her head set so that she can talk to the calling partyand ask him what number he was disconnected from.

Certain details of the system will now be explained which it was not convenient to go into before, and the first thing which will be considered is the function of the timing switch P, Fig. 3. This switch is provided for the purpose of handling the so-called mutilated calls, which are calls arriving at a register set and which, because of improper dialling by the calling subscriber, or failure of some switch to function properly, are not completely registered. It will be understood that in the ordinary operation of the system a call is displayed to the operator by the energization of relay 305 followed by the energization of relay 1 at the proper time, under the control of the consecution control switch CCS. The energization of relay 305, however is contingent on two series of impulses being transmitted to the register control switch RCSJvhich causes the switching relay 405 of the register set R to be energized to ground conductor 414; and itwill be appreciated, therefore, that if less than two digits are registered, relay 305 will not ordinarily be energized, and the partially registered number will never be displayed to the operator. Experience has shown that these incomplete calls are a fruitful source of trouble, since each such call occupies a register set until the calling subscriber hangs up his receiver, without giving the operator :1 signal of any kind. In order to eliminate Wa e when relay 306 pulls up a, circuit isclo sed for thegstepping magnet 3241 of timing switch Pat armature 320,, andthetiming switch begins to operate underithe-controlofthe ti me;con trol impulse sender, indicatedby the, referencecha'racter;" 11,; This impulse sending mechanism; -is ,so ,arrangecl,;that the con;

ductor .322 is grounded-atpnmsepond intervals with the result that after, theexpiration.

of .ten seconds the wiper331; closes a circuit by ,whichground is, connected with conduc tori A14. This causes relay 305 togbe. energized, and whatever digits ghaveebeen registered in the meantime are displayed tothe operator in due-course. It .will. be,obvious that the time interval canrbeyaried as ;de--

.- sired, but theintervalof ten seconds herein mentioned is believed towbe about right, since it has been determined. vby gobserying. alarge number ofucalls thaththis time interval is long enough to allow ordinary calls toflbe completely registered. in practically {all cases. 0t course, ifthe subscriber isvery slow in calling a number .the time interyal .w'ilthave. elapsed before he is .through,.but.,this causes no particular harm, since the vcircuit. ars

rangement is suchthat the subsequent regis tration of the digits is not interfered with. It is intended that thefmutilatedfcalls will be extended by the operator to. acomplaint or trouble operator by plugging into trunk lines provided for this purpose in order that the regular operatormay be free to confine her attention to handling the. regular trafiic.

A novel feature, consistin of an arrangement for making all truniis busy leading from an operators position, either when the operator leaves her position, or when all call register sets are in use, will now be described.

Referring to relay 108 of Fig. 1, it may be pointed out that this a gang relay, and when operated extends ground over. conductors such as 133 to each repeater of'the particular group to which it is common. Relay 108 is operated over conductor..109 leading to the manual exchange, there being one of these conductors for each group of trunk lines. Conductor 109 may be grounded at two different points to cause the operation of relay 108. First, assuming that the operator desires to leave her position, she will withdraw her plug 236 from jack 237, permitting relay 238 to be deenergized, which closes a circuit from ground, armature 250, conductor 109, and relay 108 to battery. Relay 108 energizes and, assuming that the trunk line associated with the repeater E is idle, closes a circuit from ground, armature 132 audits working contact, conductor 133, armature, 134, armaturellfl', and conductor 77 totest-conta c-ti h ILsimilar circuit is completed byarmaturs132' and132 to the test contacts of all otl1er:.-idlc trunks of the grou ,leading ,tothis particular operators position of the manual exchange.

,Attention is, called to ,the factthat if the trunk line associated with repeater E is in useatthis time it'willnot'be-elfected by the operation of 1.elay. 1( ),8.as the busying circuit willbe,in terrupted' either, at armature 134.

or 117, butjas soon (as the trunk becomes idle, armatiire 13 ta'ndj'117 will have returned ,tonorinal'and. the trunk line will be againmade busy, pioviding the gang relay 108, is still energized.

..Tl1e"- ,.otlie r,c ondtion under, which relay 10f6is' .operated is when all the register sets assigned to; the position are busy.

Referring to the relay 327 of Fig. 3, this relay ,is nQlfmally shortflcircuited by a common conductor having branches such as 340 leading to the' backf contfact of armature 319 of relay, .3( )'6 togronn d It will be seen, therefore, that the relay 327 will operate only when the, relays 1396 of all register control switches are energized, or in other words,when allthe registensetsare in use.

Assuiiiingfthis to bethec'as'e, relay 327 energizes and/grounds conductor 109, thus causing relay 108 to'opcrate and function in the same manner as hereinbefore described." ,X l Having described my jinycntion, what I consider nevi and desire tohave protected by Letters Patent will be pointed out in the appended claims.

hat I claim as my invention is 1. Ina teIephOnesystem, a manual exchange, trunk lines terminating in cord circuitsQin said exchange, automatic substations having access to said trunk lines for callingjthe subscribers in the manual exchange, a plurality of relay register sets for registering the telephone numbers of called manual stations, and an automatic switch for each of said cord circuits for connecting its associated cord circuit with an idle register set when the cordcircuit is taken for use, and means for preselectingidle register sets ahead of the calls. I x

2. In a telephone system, a manual ex change, trunk lines terminatin in cord circuits in said exchange, automatic substations having access to said trunk lines for calling the subscribers in the manual exchange, a plurality of register sets for registering the telephone numbers of called manual stations, an automatic switch for each of said cord circuits for connecting its associated cord circuit with an idle preselected register set when the 00rd circuit is taken for use, and

registering the telephone numbers of called:

manual stations, an automatic switch for each of said cord circuits'for connecting its associated cord circuit with an idle preselected register set when the cord circuitjs taken for use, and means for pie-selecting idle register sets ahead of the calls. 1

t. In a telephone system, a manual exchange and anautomatic exchange,"a trunk line accessible to automatic switches in the automatic exchange and terminating in a' cord circuit in the manual exchange, a regis-, ter set compr sing a'serles of relay "groups for registering the numbers of manuallines called over said trunk'line, a,switch individual to said cord'c ircuit for extending a connection to the Said register set when a line is being called, a register control switch,

and a relay in said cord circuit for repeated-' ly operating said control switch to successively control the setting of said relay groups.

in said automatic exchange terminating ,in a cord circuit at said manual exchange, call.

register sets comprising relay groups, a line switch associated-with. said cord circuit, a master-switch for pre-selecting an idle register set, and means responsive to the seizure of said cord circuit for causing said line switch to seize the preselected register set.

6. In a telephone system, an automatic exchange, a manual exchange, trunk lines extending from said automatic to said manual exchange, call register sets in said manual exchange accessible to said trunk lines, a relay in said automatic exchange common to said trunk lines, a conductor extending from the automatic to the manual exchange, and means at the manual exchange operated when all the register sets are in use for causing the energization of said relay over said conductor to make all of said trunk lines busy.

7. In a telephone system, two conductor trunk lines extending from an automatic to a manual exchange, a relay at the automatic exchange for making all of said trunk lines busy when energized, and means at the manual exchange operable automatically to cause the energization of said relay, said means including a second. relay common to said trunk lines.

8. In a telephone system, an automatic exchange, and a manual exchange, trunk lines comprising only two conductors extending from said automatic to said manual exfor'making all of the busy trunks artificiallybusy as soon'as they become idle. 7

'9. In a register set, a plurality of; groups of ip'erl'nutational relays, an automatic switch, means for-operatingand releasing sa id 's ivitch fi 'pluralit 'y of times 'inaccordance with afFplurality of digits in called number, and Trn eans including' a wiper in a Switch 1- ro1li'ng? the setting of said relay groupssuccessivelyl l "10. -Ina"'register=set,"a 'plurality bf grou s of perniiitationa; relays; =';-'-an -"atitomatic switch, means ffor' operating and releasing said switch a plurality of times n accordafiee with a plurality of"'digits in a called numberfim'ean 'fiiiclti' ing" a iper in said switch, for, 'c'ontrolling the'setting of said riay'geo'a seae essiveiyyan a set oi digit ifi'diea'tors'eohcrellea aid relay "groups for displaying the called "'ilii inberi In" a registerset, aplu'rality of groups o'f- ."permutatit'ina1, frela'ys, an automatic switch, means "for" operating and releasing said switch atiilurality'i'of times in accordance" with a plurality of digits -in-a'called number, means including a" wiper" in said switch for; controlling 'the' setti'ng ofsaid relay'grdupsuccessively,a group of lamps associated with ea'chrelay group,- and'contacts controlled? by actuatedrelays in 'said groups, 'for"lighting "a particular lamp in eachjgroup to' disp'la'y'the called number.

12. In a register set, a series of digit lamps, ipermutation'al relays less in number than said lamps operable singly and in combination to light any desired lamp, and an automatic switch controlled by a'calling subscriber inaccordance witha digit in a called number to selectively operate said relays as set forth.

13. In a telephone system, an automatic exchange, a manual exchange, trunk lines extending from said automatic exchange to said manual exchange, call register sets in said manual exchange accessible to said trunk lines, a normally deenergized relay in said automatic exchange common't-o said trunk lines, a conductor extending from the automatic exchange to the manual exchange, means at the manual exchange operated when all the register sets are in use for caus ing the operation of said relay over said conductor, and means controlled by said relay for making all of said trunk lines busy.

14; In a telephone system, trunk lines extending from an automatic to a manual exchange, automatic switches having access to said trunk lines, a relay at the automatic exchange having a set of contacts for each trunk line efiective when said relay is operated to make said trunks busy to said automatic switches, illCi means including a conductor common to said trunk lines for autcmatically causing the operation of said relay.

15. In a telephone system. trunk lines extending between an automatic and a manual exchange, a relay at the automatic exchange having a set of contacts for each trunk line, efiectivc when said relay is energized, to make said trunk lines busy, and means at the manual exchange operable automatically to cause the energization of said relay.

16.'In a register set, a plurality of groups of permutational relays, an automatic switch having access to conductors extending to relays of one of said groups, means for operating said switch in accordance with a digit in .3, called number, means for completing circuits for one or more of the permutational relays of the connected group following the operation of said switch, and means controlled over said circuits for releasing said switch and for transferring the conductors accessible to said switch to relays of a second one of said groups, said first'means being then elfe'ctive for reoperating said switch in accordance with a second digit of a called number for closing energizing circuits for one or more relays of said second group.

17. In a register set, a plurality of groups of relays, a switch responsive to successive series of impules, circuits selected by said switch each time it is operated to energize a particular permutation of one or more relays, and means operated after each series of impulses for causing the circuits selected by the next series to include relays of the next group.

18. In a register set, a series of ten digit lamps, four relays operable singly and in digit in a called number to selectively operate said relays as set forth.

19. In a register set, ten lamps all connected to the same pole of a source of current, ten conductors terminating in said lamps, re spectively, a plurality of relays less in numher than the number of said conductors oper able singly and in combination for selecting any of said conductors, and means for selectively operating said relays as set forth.

20. In a telephone system, trunk lines each comprising only two conductors extending from an automatic exchange to a manual exchange, a conductor common to said trunk lines, a relay at the automatic exchange for making all said trunks busy when energized, a second relay at said manual exchange common to said trunk lines, and contacts on said second relay adapted when closed to close a circuit over said common conductor to energize said first relay.

21. In a telephone system, a manual exchange, an automatic exchange, a trunk line in said automatic exchange-extending to and terminating in said manual exchange, call register sets comprising relay groups in said manual exchange, a lineswitch in said manual exchange associated with said trunk line, a master switch for preselecting an idle reg ister set, and means responsive to the seizure of said trunk line at said automatic exchange for causing said lineswitch in the manual exchange to seize the pre-selected registerset.

In witness whereof, I hereunto subscribe my name this 6th day of May, A. D., 1922.

BERNARD D. WILLIS. 

